We can dynamically adjust the grid layout based on the number of cards on the board. Here's how we can modify the component to achieve this:

1. First, let's create a function to determine the appropriate grid class:

2. Now, let's update the return statement to use this function:

3. We should also update the addThreeCards function to ensure it doesn't add cards if there are already more than 12 on the board:

4. Finally, let's modify the handleValidSet function to maintain at least 12 cards on the board if possible:

These changes will:

1. Keep the 4-column layout when there are 12 or fewer cards.
2. Expand to a 5-column layout only when there are more than 12 cards.
3. Ensure that the "Add 3 Cards" button only works when there are 12 or fewer cards on the board.
4. Maintain at least 12 cards on the board after a valid set is removed, as long as there are cards left in the deck.

This approach should give you the desired behavior: the board will only expand to 5 columns when necessary, and it will try to maintain at least 12 cards on the board at all times.

While your current implementation works well as a single file, splitting it up can improve maintainability and readability, especially as the project grows. Here's how you could structure it according to Next.js and App Router best practices:

1. Main Component File (app/page.tsx): Keep the main SetGame component here, but move most of the logic to separate files.
2. Game Logic (lib/game-logic.ts): Move functions like createDeck, isSet, and findSet here.
3. Types (types/index.ts): Define your types and interfaces here.
4. Hooks (hooks/useSetGame.ts): Create a custom hook for game state and logic.

5. Components (components/):

   • Card.tsx: Move the card rendering logic here.
   • GameBoard.tsx: Create a component for the game board.
   • ScoreBoard.tsx: Create a component for displaying score and time.

Here's a suggested structure:

Here's how you might implement this:

1. app/page.tsx

The other files (hooks/useSetGame.ts, lib/game-logic.ts, etc.) would contain the respective logic that's currently in your single file.

This structure separates concerns, making the code more maintainable and easier to test. However, for a relatively simple game like this, keeping it in a single file is not necessarily bad practice, especially if it's not expected to grow significantly in complexity.

The decision to split the code should be based on your specific needs, team preferences, and the expected future complexity of the project. If you find the current structure manageable and don't anticipate significant additions, keeping it as a single file is perfectly acceptable.